Variability of the geomorphometric characteristics of Makkah Al-Mukaramah basins in Saudi Arabia and the impact on the hydrologic response

Abstract

Statistical analyses are performed on the geomorphological characteristics of Makkah Al-Mukaramah basins. The purpose of these analyses is to study the variability of the geomorphological characteristics (13 parameters) and their effects on the variability of the hydrological and kinematic response (6 variables). Different probability density functions (PDF) of the prevailing morphometric variables are tested. The Kolmogorov–Smirnov test is utilized for the goodness of fit test to find the best PDF together with Akaike Information Criterion to assess various best fits. The statistical analyses revealed that the highest coefficient of variation (CV = 1.43) is for peak discharge of the geomorphological instantaneous unit hydrograph (GIUH). Apparently, this is due to the high CV (1.14) for the length of the highest order stream. The lowest CV(0.07) is observed for the similarity parameter of basins. This indicates a high similarity between the basins from the geomorphological point of view. The PDF analyses show that the morphological and hydrological variables display different probability distribution patterns. Based on the geomorphoclimatic instantaneous unit hydrograph GCIUH, it has been shown that there is a high variability in the basin response as a result of an exponential distribution of rainfall intensity and duration. Peak discharge and time to peak have a practical truncations of the distribution tail at 0.5 h−1and 10 h, respectively. The quartile classification of the basins shows that some variables have distinct clusters, while others show almost no clustering at all. The study provides assessment of the potential flood risk and the potential recharge basins in the study area.